1. Field of the Invention
This invention relates to sealing elements such as grommets for use in isolating structural members, such as for use in aircraft electrical systems or tubing feed-throughs, such as those where tubing or electrical cables penetrate the web of a structural member or containment wall. In one specific application, the invention relates to a grommet which maintains electrical continuity between a tube or cable and a structure through which the tube or cable passes, such as a metal panel, bulkhead or the like.
2. Related Art
Single piece elastomer grommets are commonly used for cable and tubing penetrations in aircraft and other industries. However, the use of single piece elastomer grommets is typically limited to standard specification applications other than those requiring electrical conductivity.
Electrical continuity is important in aircraft safety in order to protect aircraft systems from damage caused by electrical faults, lightning strikes and other forms of electromagnetic interference (EMI). Fire and pressure containment is also important to protect personnel and equipment and to minimize the effect on the overall aircraft by fire in one location or pressure differentials between two locations. Single piece elastomer grommets have served the function of pressure and fire containment but do not protect against EMI.
Current methods of maintaining electrical continuity, pressure sealing and fire containment use a metal bulkhead fitting consisting of threaded metal pieces and a rubber insert. These fittings can often be quite complex, consisting of between 3 and 18 or more pieces. These fittings are relatively heavy, have a relatively high cost and require a relatively lengthy time for installation. Often, these fittings require use of a sealant to protect the joint against galvanic corrosion and other environmental effects. These fittings also require substantial testing to ensure proper sealing and electrical continuity. If repair or replacement is required, the fitting must be removed, the surrounding area cleaned and a new fitting and seal installed, again requiring a substantial amount of time and effort.
In conventional fittings, the fitting can accommodate only a single cable, or cable bundle where more than one cable is bundled into a single assembly. As a result, multiple cables may be combined into a bundle for purposes of passing through the fitting, even though their function or final location in an aircraft, for example, may be unrelated. Multiple cables are often bundled basically because of limitations in fitting arrangements, as opposed to because of the locations where the cables will end up or the cable functions.